Lead acid batteries have evolved, over time, as the demands for a source of mobile electric power have grown. There are two main types of lead acid batteries: flooded lead acid batteries and VRLA (valve regulated lead acid) batteries. The instant disclosure may be particularly useful for flooded batteries, which are commonly used all over the world. A newer type of flooded lead acid battery is an EFB battery, or an enhanced flooded battery. For example, the new, ever growing requirements for Stop Start car technology demands a better battery which may be the “enhanced” flooded battery, or EFB.
Water loss in lead acid batteries is a known problem (loss of water from the electrolyte due to electrolysis producing hydrogen and oxygen gas that vents from the battery) and may occur for many different reasons. For example, water loss may occur in lead acid batteries as the overvoltage of hydrogen is exceeded at the electrodes. This may be typical and may occur to some extent as the electrochemical mechanism dictates. The effects of water loss may be greatly amplified in climates with sustained high temperature. Water loss has been identified as a major contributor to the following critical failure modes in lead acid batteries: plate dehydration, which may lead to battery failure; dryout in a sealed VRLA battery, which may lead to potential thermal runaway; negative plate sulfation, which may lead to reduced charge acceptance and/or reduced cycle life; and/or increased specific gravity of electrolyte, which may lead to negative plate sulfation and/or positive grid corrosion.
Water loss in a lead acid battery can be seen through: reduced level of electrolyte leading to dryout, exposing welds, plates and connections to corrosion and causing early failure; increasing electrolyte acid concentration, reduced capacity, negative plate sulfation, positive grid corrosion leading to early failure; and/or outgassing of H2 and O2 gasses, possibly creating an exposure and handling hazard and requiring venting. As such, reducing water loss in lead acid batteries may help eliminate: plate dehydration leading to early capacity loss and shortened life; negative plate sulfation, reducing life; and/or positive grid corrosion, reducing performance by robbing CCA (cold cranking amperage) and capacity and life. Water loss from lead acid batteries may be mainly due to electrolysis and subsequent gassing of hydrogen and oxygen, which may be more apparent in high temperature climates or applications.
EFBs may suffer from any of these water loss scenarios, including evaporation and electrolysis of water. Water loss, whether through evaporation and/or electrolysis, is commonly known to lower the performance and/or life of the EFB. As such, many methods have been developed to combat this drawback, including VRLA/AGM type batteries. However, even in a sealed VRLA/AGM battery, for example, the potential for dryout is present, and a potential thermal runaway could occur because of water loss. Thus, it can be said that various known and/or already-developed methods of combatting water loss in lead acid batteries may not provide all of the desired improvement in reduction in water loss and may require high costs that may not match the value brought forth by various developed methods.
As such, there is clearly a need to develop lead acid batteries and systems and vehicles including such lead acid batteries with improved water loss performance, and/or the ability to reduce evaporation and/or electrolysis of water in a flooded lead acid battery that is cost effective.